How do I move videos on and off the cloud?

In order to "move them to the cloud" simply delete them from the iPad. You can do that in the videos app by tapping on the Edit button in the upper right corner of the Movies or TV shows tabs. You can also delete them in Settings>General>Usage>Storage>Videos. You can use the Edit button there or swipe from righ to left across the videos in the list to get the red delete button.

In order to move them back to the iPad, you just download them again. You can do that in the purchased tab of iTunes or you can go to Settings>iTunes and App Stores>Show All>Videos>On. All of the videos in the cloud will appear in the videos app and you can tap the cloud icon if you want to download them again.

You do want to make sure that the movies are still available in iTunes before you delete them and even though Apple offers the use of iCloud for this very purpose that you want. it makes more sense if you keep all of your purchased content in your iTunes library on your computer. You are better off having control of your content than leaving it in Apple's hands - IMHO.